Channel Estimation in a Radio Receiver

1. Receiver apparatus for computing channel estimates from a received signal having a slotted structure, each slot comprising a sequence of data symbols and a sequence of pilot symbols, the receiving apparatus including: M summers for respectively summing the pilot symbols of each of M slots, where M is greater than 1 and the M summers produce respective M outputs x(i); J interpolation filters each arranged to receive the outputs x(i) as inputs, where J specifies a chosen number of time instances of one of the M slots; a computation module connected to each of the J interpolation filters for computing respective filter coefficients, Fj,i, therefor depending upon the chosen number of time instances Tj relating to said one of the M slots, time instances of the pilot symbols and a chosen polynomial interpolation order N greater than 2; whereby each of the J interpolation filters is configured to compute a channel estimate, ChanEst j = ∑ i = 0 M - 1 ⁢ F j , i ⁢ x ⁡ ( i ) for one of said chosen number of time instances Tj, where j takes a value 0, . . . , J−1.

2. The apparatus according to claim 1 , in which the filter co-efficients F j,i are computed in accordance with the relationship; F j , i = ∑ k = 0 N - 1 ⁢ ⁢ b k . i ⁡ ( T ) k where b k,i is a (k, i) th element of a matrix B, which relates to time instances of the pilot symbols; where P=BX; and where P is an interpolation polynomial of an order, N, and X is a vector representing the M outputs, x(i).

3. The apparatus according to claim 1 in which M=4 and j=4.

4. The apparatus according to claim 1 , wherein the chosen number of time intervals of the M slots is greater than 1.

5. A method of computing channel estimates from a received signal having a slotted structure, each slot comprising a sequence of data symbols and a sequence of pilot symbols, the method including: respectively summing the pilot symbols of each of the M slots using M summers to produce respective M outputs x(i), where M is greater than 1; choosing a number of time instances J of one of the M slots; providing J interpolation filters, each of the J interpolation filters receiving the M outputs x(i) as inputs; computing respective filter coefficients, Fj,i, for each of the J interpolation filters depending upon the chosen number of time instances Tj relating to said one of the M slots, time instances of the pilot symbols and a chosen polynomial interpolation order N greater than 2; and computing, within each of the J interpolation filters, a channel estimate, ChanEst j = ∑ i = 0 M - 1 ⁢ F j , i ⁢ x ⁡ ( i ) for one of said chosen number of time instances Tj, where j takes a value 0, . . . , J−1.

6. The apparatus according to claim 1 , further arranged to combine the computed channel estimates with a Common Pilot Channel (CPICH) estimation to produce a refined channel estimation.

7. The apparatus according to claim 6 , wherein the chosen number of time intervals of the M slots is greater than 1.

8. The apparatus according to claim 1 , further arranged to use the computed channel estimates to provide a quasi-pilot for a second iteration to produce a refined channel estimation.

9. The apparatus according to claim 8 , wherein the chosen number of time intervals of the M slots is greater than 1.

10. The apparatus according to claim 1 , further arranged to combine the computed channel estimates with an inter-path cancellation scheme.

11. The apparatus according to claim 10 , wherein the chosen number of time intervals of the M slots is greater than 1.

12. The apparatus according to claim 1 , wherein the J interpolation filters are arranged to generate J corresponding channel estimates respectively relating to the time instances Tj chosen.

13. The apparatus according to claim 12 , wherein the chosen number of time intervals of the M slots is greater than 1.

14. The method according to claim 5 , wherein the chosen number of time intervals of the M slots is greater than 1.

15. The method according to claim 5 , further comprising: combining the computed channel estimates with a Common Pilot Channel (CPICH) estimation to produce a refined channel estimation.

16. The method according to claim 15 , wherein the chosen number of time intervals of the M slots is greater than 1.

17. The method according to claim 5 , further comprising: using the computed channel estimates to provide a quasi-pilot for a second iteration to produce a refined channel estimation.

18. The method according to claim 17 , wherein the chosen number of time intervals of the M slots is greater than 1.

19. The method according to claim 5 , further comprising: combining the computed channel estimates with an inter-path cancellation scheme.

20. The method according to claim 5 , further comprising: the J interpolation filters generate J corresponding channel estimates respectively relating to the time instances Tj chosen.